Started the NHA stack (Activate and Rebounded Reloaded). Would taking Mega Hoodia and Syneburn in the evenings to help control the appetite have any effect on the results of the NHA stack?

I think you answered your own question allready! But it also depends on what your goals from this stack are( I'm taking a wild guess here and saying you are cutting up or trying to lose weight a/ keep muscle). If cutting and hardening up is your goal, then these additions to the NHA stack could make that goal easier. If you are trying to gain mass, then obviously these would not be a good addition, cause you are not going to be able to consume the extra(clean) calories you would need.